1. Field of the Invention
This invention relates to multicomponent membranes for gas separations.
2. Prior Art
Membranes suitable for separating one gas from a mixture of gases are known, including multicomponent membranes formed as hollow fibers and made up of a porous substrate layer supporting a thinner and less porous layer. In any type of membrane to be used for gas separations, it is desirable that the membrane have the highest permeability possible for the one gas to be separated from the mixture and the greatest separation factor for that gas with respect to other gases of the mixture. In other words, the one gas to be separated should permeate the membrane at the highest possible rate, while the other gases of the mixture should permeate the membrane at the lowest possible rate. Unfortunately, any gains made in increasing either the permeability or the separation factor of the membrane usually result in a reduction of the other. It would be desirable to improve either one of the permeability or separation factor of the membrane without sacrificing the other.
U.S. Pat. No. 4,230,463 discloses a multicomponent membrane which is in the form of a hollow fiber, the hollow fiber consisting of a porous substrate layer and a thinner less porous layer on the substrate layer. In preferred examples, the substrate layer is polysulfone and the coating layer is poly(dimethyl siloxane).